Thanks Yonghong,
Sorry for the delay in here.
I have split commits into 3 as you asked. Will send it out shortly. Have few questions below re: find_vma test.
> On Mar 3, 2022, at 12:31 PM, Yonghong Song <yhs@xxxxxx> wrote:
>
>
>
> On 3/3/22 9:29 AM, Mykola Lysenko wrote:
>>> On Mar 3, 2022, at 7:36 AM, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>>>
>>> On 3/2/22 10:27 PM, Mykola Lysenko wrote:
>>>> In send_signal, replace sleep with dummy cpu intensive computation
>>>> to increase probability of child process being scheduled. Add few
>>>> more asserts.
>>>> In find_vma, reduce sample_freq as higher values may be rejected in
>>>> some qemu setups, remove usleep and increase length of cpu intensive
>>>> computation.
>>>> In bpf_cookie, perf_link and perf_branches, reduce sample_freq as
>>>> higher values may be rejected in some qemu setups
>>>> Signed-off-by: Mykola Lysenko <mykolal@xxxxxx>
>>>> Acked-by: Yonghong Song <yhs@xxxxxx>
>>>> ---
>>>> .../selftests/bpf/prog_tests/bpf_cookie.c | 2 +-
>>>> .../testing/selftests/bpf/prog_tests/find_vma.c | 13 ++++++++++---
>>>> .../selftests/bpf/prog_tests/perf_branches.c | 4 ++--
>>>> .../selftests/bpf/prog_tests/perf_link.c | 2 +-
>>>> .../selftests/bpf/prog_tests/send_signal.c | 17 ++++++++++-------
>>>> .../selftests/bpf/progs/test_send_signal_kern.c | 2 +-
>>>> 6 files changed, 25 insertions(+), 15 deletions(-)
>>>> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
>>>> index cd10df6cd0fc..0612e79a9281 100644
>>>> --- a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
>>>> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
>>>> @@ -199,7 +199,7 @@ static void pe_subtest(struct test_bpf_cookie *skel)
>>>> attr.type = PERF_TYPE_SOFTWARE;
>>>> attr.config = PERF_COUNT_SW_CPU_CLOCK;
>>>> attr.freq = 1;
>>>> - attr.sample_freq = 4000;
>>>> + attr.sample_freq = 1000;
>>>> pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
>>>> if (!ASSERT_GE(pfd, 0, "perf_fd"))
>>>> goto cleanup;
>>>> diff --git a/tools/testing/selftests/bpf/prog_tests/find_vma.c b/tools/testing/selftests/bpf/prog_tests/find_vma.c
>>>> index b74b3c0c555a..7cf4feb6464c 100644
>>>> --- a/tools/testing/selftests/bpf/prog_tests/find_vma.c
>>>> +++ b/tools/testing/selftests/bpf/prog_tests/find_vma.c
>>>> @@ -30,12 +30,20 @@ static int open_pe(void)
>>>> attr.type = PERF_TYPE_HARDWARE;
>>>> attr.config = PERF_COUNT_HW_CPU_CYCLES;
>>>> attr.freq = 1;
>>>> - attr.sample_freq = 4000;
>>>> + attr.sample_freq = 1000;
>>>> pfd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC);
>>>> return pfd >= 0 ? pfd : -errno;
>>>> }
>>>> +static bool find_vma_pe_condition(struct find_vma *skel)
>>>> +{
>>>> + return skel->bss->found_vm_exec == 0 ||
>>>> + skel->data->find_addr_ret != 0 ||
>>>
>>> Should this not test for `skel->data->find_addr_ret == -1` ?
>> It seems that find_addr_ret changes value few times until it gets to 0. I added print statements when value is changed:
>> find_addr_ret -1 => initial value
>> find_addr_ret -16 => -EBUSY
>> find_addr_ret 0 => final value
>> Hence, in this case I think it is better to wait for the final value. We do have time out in the loop anyways (when “i" reaches 1bn), so test would not get stuck.
>
> Thanks for the above information. I read the code again. I think it is more complicated than above. Let us look at the bpf program:
>
> SEC("perf_event")
> int handle_pe(void)
> {
> struct task_struct *task = bpf_get_current_task_btf();
> struct callback_ctx data = {};
>
> if (task->pid != target_pid)
> return 0;
>
> find_addr_ret = bpf_find_vma(task, addr, check_vma, &data, 0);
>
> /* In NMI, this should return -EBUSY, as the previous call is using
> * the irq_work.
> */
> find_zero_ret = bpf_find_vma(task, 0, check_vma, &data, 0);
> return 0;
> }
>
> Assuming task->pid == target_pid,
> the first bpf program call should have
> find_addr_ret = 0 /* lock irq_work */
> find_zero_ret = -EBUSY
>
> For the second bpf program call, there are two possibilities:
> . irq_work is unlocked, so the result will find_addr_ret = 0, find_zero_ret = -EBUSY
> . or irq_work is still locked, the result will be find_addr_ret = -EBUSY, find_zero_ret = -EBUSY
>
> the third bpf program call will be similar to the second bpf program run.
>
> So final validation check probably should check both 0 and -EBUSY
> for find_addr_ret.
>
Do you mean we need to add additional test in test_and_reset_skel function or in find_vma_pe_condition?
Do we really need to do final check for skel->data->find_addr_ret in test_and_reset_skel if we already confirmed
It became 0 previously?
> Leaving some time to potentially unlock the irq_work as in the original
> code is still needed to prevent potential problem for the subsequent tests.
By leaving some time, do you mean to revert removal of the next line in serial_test_find_vma function?
usleep(100000); /* allow the irq_work to finish */
>
> I think this patch can be broke into three separate commits:
> - find_vma fix
> - send_signal fix
> - other
> to make changes a little bit focused.
>
>> TL:DR change in the test that prints these values
>> - for (i = 0; i < 1000000000 && find_vma_pe_condition(skel); ++i)
>> + int find_addr_ret = -1;
>> + printf("find_addr_ret %d\n", skel->data->find_addr_ret);
>> +
>> + for (i = 0; i < 1000000000 && find_vma_pe_condition(skel); ++i) {
>> + if (find_addr_ret != skel->data->find_addr_ret) {
>> + find_addr_ret = skel->data->find_addr_ret;
>> + printf("find_addr_ret %d\n", skel->data->find_addr_ret);
>> + }
>> ++j;
>> + }
>> +
>> + printf("find_addr_ret %d\n", skel->data->find_addr_ret);
>>>
>>>> + skel->data->find_zero_ret == -1 ||
>>>> + strcmp(skel->bss->d_iname, "test_progs") != 0;
>>>> +}
>>>> +
>>> Thanks,
>>> Daniel
